Portable personal computers (PCs) were first introduced in the early 1980s and have since enjoyed great commercial success and consumer acceptance. As the portable PC market has grown, users have begun to demand lighter weight, lower volume PCs that can be used for longer periods of time between battery charges. Meeting these demands has proved challenging in view of the fact that most portable PCs now support peripheral devices previously available only on desktop PCs. The additional peripherals greatly increase overall power consumption, making it difficult to achieve an optimal level of functionality while maintaining an acceptable battery life. Furthermore, although for reasons other than maximizing battery life, it has become desirable to more efficiently manage power consumption of desktop PCs in order to minimize overall operating costs.
One way to reduce the power consumption of a PC is to implement certain PC components as mixed voltage devices that are capable of operating at 5 volts, 3.3 volts, or some other as yet unspecified reduced voltage level. An example of such a mixed voltage device is the Vadem VG-469 ("VG-469") PC card controller, commercially available from Vadem Corporation of San Jose, Calif. A key feature of the VG-469 is that it allows PC cards to run in 5- and 3.3-volt, as well as future lower voltage, systems. In order to safely implement this feature, the VG-469 has a proprietary hardware mechanism that protects lower voltage cards from damage when used in 5-volt systems. Specifically, the VG-469 is designed such that it resets to 3.3 volts. Consequently, in order for it to recognize 5-volt cards, it must be set back to 5 volts. While this feature does indeed protect 3.3-volt cards from damage due to high voltage levels, in view of the fact that the vast majority of PC cards currently available operate at 5, rather than 3.3, volts, some means must be provided for recognizing 5-volt cards and setting the VG-469 accordingly.
In a DOS environment, such recognizing and setting functions are performed by a driver that checks the voltage level of a PC card inserted into a PC card slot and then sets the VG-469 accordingly. However, in the presence of operating systems ("OSs") such as Windows 95, Windows NT, OS/2 and others, that have embedded drivers, and therefore ignore the DOS drivers, such a mixed voltage feature is not presently supported. Hence, when a secure OS such as those previously listed starts up, the VG-469 will reset to 3.3 volts and, because the OS does not support mixed voltage technology, only 3.3-volt cards will be recognized and operable. As a result, users will be able to use their 5-volt cards under DOS, but not under secure OSs, which are becoming increasingly popular.
Therefore, what is needed is an OS-independent mechanism for handling advances in hardware technology, such as mixed voltage devices, that are not supported by the OS of the computer in which such technology is implemented.